let welcome='hello'
welcome()

const str = Date.now() %2 ?'奇数':'偶数'
if(str !== '奇数'){
    alert('hello')
}else if(str === '偶数'){
     alert('world')
}


const obj ={width:10,height:20}
const area=obj.width*obj.heighh


const xx = 'helloworld'
xx.toUperCase()